nimble/ll: Fix rfclk after extended scan stop

It's quite possible that when stopping extended scan we also remove some
AUX scan items form scheduler so we should trigger rfclk to restart on
proper item.

nimble/controller/src/ble_ll_scan.c

@@ -1270,7 +1270,6 @@ ble_ll_scan_sm_stop(int chk_disable)
     if (scansm->ext_scanning) {
         ble_ll_scan_clean_cur_aux_data();
         ble_ll_sched_rmv_elem_type(BLE_LL_SCHED_TYPE_AUX_SCAN, ble_ll_scan_sched_remove);
-        scansm->ext_scanning = 0;
     }
 #endif
 
@@ -1304,6 +1303,15 @@ ble_ll_scan_sm_stop(int chk_disable)
         }
         OS_EXIT_CRITICAL(sr);
     }
+
+#if MYNEWT_VAL(BLE_LL_CFG_FEAT_LL_EXT_ADV)
+    if (scansm->ext_scanning) {
+#ifdef BLE_XCVR_RFCLK
+        ble_ll_sched_rfclk_chk_restart();
+#endif
+        scansm->ext_scanning = 0;
+    }
+#endif
 }
 
 static int